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  MO17 - Radiotherapy I: Stereotactic Ablative Body Radiotherapy (ID 106)

  • Event: WCLC 2013
  • Type: Mini Oral Abstract Session
  • Track: Radiation Oncology + Radiotherapy
  • Presentations: 1
  • Moderators:M. Zwitter, S.K. Vinod
  • Coordinates: 10/29/2013, 16:15 - 17:45, Bayside 204 A+B, Level 2

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    MO17.03 - Incidental Prophylactic Nodal Irradiation and Patterns of Nodal Relapse in Inoperable Early Stage NSCLC Patients Treated with SBRT: A Case-Matched Analysis (ID 2024)

    16:15 - 17:45  |  Author(s): L. Lao
    • Abstract
    • Presentation
    • Slides

    Background
    Reported non-small cell lung cancer (NSCLC) nodal failure rates following stereotactic body radiotherapy (SBRT) are lower than those reported in the surgical series when matched for stage. We hypothesize that this effect is due to incidental prophylactic nodal irradiation.

    Methods
    A prospectively collected group of medically inoperable early stage NSCLC patients (n=179) from 2004 to 2010 was used to identify a patient cohort with nodal relapses (n=19). These cases were matched, 1:2, to controls, controlling for tumour volume (i.e. same or greater) and tumour location (i.e. same lobe). Reference (normalized total) point doses at the ipsilateral hilum and carina, demographic data, and clinical outcomes were extracted from the medical record. Multivariate logistical regression analyses determined variables of interest.

    Results
    The case and control cohorts were well matched with respect to age, sex, method of nodal staging, SUVmax, histology subtype, dose and length of follow up.. The controls, as expected, had larger gross tumour volumes (p=0.02). The mean hilar doses were 9.6 and 22.4 Gy for cases and controls, respectively (p=0.014). Similarly, the mean carinal doses were 7.0 and 9.2 Gy, respectively (p=0.13). The mean ipsilateral hilar doses were 19.8 and 3.6 Gy for ipsilateral non-hilar and hilar nodal relapses, respectively (p=0.01). The conditional density plot appears to demonstrate an inverse dose-effect relationship between ipsilateral hilar normalized total dose and risk of ipsilateral hilar relapse (Figure 1).Figure 1

    Conclusion
    Incidental hilar dose greater than 20 Gy (normalized to 2Gy/fraction) appears to be correlated with lack of hilar relapses in inoperable early stage NSCLC patients treated with SBRT.

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